Surgical navigation systems including reference and localization frames

ABSTRACT

A system for use during a medical or surgical procedure on a body. The system generates an image representing the position of one or more body elements during the procedure using scans generated by a scanner prior or during the procedure. The image data set has reference points for each of the body elements, the reference points of a particular body element having a fixed spatial relation to the particular body element. The system includes an apparatus for identifying, during the procedure, the relative position of each of the reference points of each of the body elements to be displayed. The system also includes a processor for modifying the image data set according to the identified relative position of each of the reference points during the procedure, as identified by the identifying apparatus, said processor generating a displaced image data set representing the position of the body elements during the procedure. The system also includes a display utilizing the displaced image data set generated by the processor, illustrating the relative position of the body elements during the procedure. Methods relating to the system are also disclosed. Also disclosed are devices for use with a surgical navigation system having a sensor array which is in communication with the device to identify its position. The device may be a reference frame for attachment of a body part of the patient, such as a cranial reference arc frame for attachment to the head or a spine reference arc frame for attachment to the spine. The device may also be a localization frame for positioning an instrument relative to a body part, such as a localization biopsy guide frame for positioning a biopsy needle, a localization drill guide assembly for positioning a drill bit, a localization drill yoke assembly for positioning a drill, or a ventriculostomy probe for positioning a catheter.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The system and frames of the invention are improvements upon thesystem described in U.S. patent application Ser. No. 08/053,076, filedApr. 26, 1993 and its continuation, Ser. No. 08/524,981, filed Sep. 7,1995. The entire disclosure of Ser. No. 08/053,076 and its continuationSer. No. 08/524,981, are incorporated herein by reference. In addition,this invention is an improvement upon Ser. No. 08/319,615, filed Oct. 7,1994, the entire disclosure of which is incorporated herein byreference. In addition, this invention is an improvement uponprovisional application Serial No. ______ (to be assigned), filed Sep.8, 1995, the entire disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] The invention relates generally to systems which use and generateimages during medical and surgical procedures, which images assist inexecuting the procedures and indicate the relative position of variousbody parts and instruments. In particular, the invention relates to asystem for generating images during medical and surgical proceduresbased on a scan taken prior to or during the procedure and based on thepresent position of the body parts and instruments during the procedure.

[0003] Image guided medical and surgical procedures comprise atechnology by which scans, obtained either pre-procedurally orintra-procedurally (i.e., prior to or during a medical or surgicalprocedure), are used to generate images to guide a doctor during theprocedure. The recent increase in interest in this field is a directresult of the recent advances in scanning technology, especially indevices using computers to generate three dimensional images of parts ofthe body, such as computed tomography (CT) or magnetic resonance imaging(MRI).

[0004] The majority of the advances in diagrammatic imaging involvedevices which tend to be large, encircle the body part being imaged, andare expensive. Although the scans produced by these devices depict thebody part under investigation with high resolution and good spatialfidelity, their cost usually precludes the dedication of a unit to beused during the performance of procedures. Therefore, image guidedsurgery is usually performed using images taken preoperatively.

[0005] The reliance upon preoperative images has focused image guidancelargely to the cranium. The skull, by encasing the brain, serves as arigid body which largely inhibits changes in anatomy between imaging andsurgery. The skull also provides a relatively easy point of reference towhich fiducials or a reference system may be attached so thatregistration of pre-procedural images to the procedural work space canbe done simply at the beginning, during, or throughout the procedure.Registration is defined as the process of relating pre-procedural orintra-procedural scan of the anatomy undergoing surgery to the surgicalor medical position of the corresponding anatomy. For example, see Ser.No. 07/909,097, now U.S. Pat. No. 5,383,454 the entire disclosure ofwhich is incorporated herein by reference.

[0006] This situation of rigid fixation and absence of anatomicalmovement between imaging and surgery is unique to the skull andintracranial contents and permits a simple one-to-one registrationprocess as shown in FIG. 1. The position during a medical procedure orsurgery is in registration with the pre-procedural image data setbecause of the absence of anatomical movement from the time of the scanuntil the time of the procedure; in effect, the skull and it'sintracranial contents comprise a “rigid body,” that is, an object whichdoes not deform internally. In almost every other part of the body thereis ample opportunity for movement within the anatomy which degrades thefidelity by which the pre-procedural scans depict the intra-proceduralanatomy. Therefore, additional innovations are needed to bring imageguidance to the rest of the body beyond the cranium.

[0007] The accuracy of image guided surgery relies upon the ability togenerate images during medical and surgical procedures based on scanstaken prior to or during the procedure and based on the present positionand shape of the body parts during the procedure. Two types of bodyparts are addressed herein: 1) structures within the body that do notchange shape, do not compress, nor deform between the process of imagingand the medical procedure, which are termed “rigid bodies,” and areexemplified by the bones of the skeleton; and 2) structures within thebody that can change shape and deform between the process of imaging andthe medical procedure structures are termed “semi-rigid bodies,” and areexemplified by the liver or prostate. Both types of body parts arelikely targets for medical or surgical procedures either for repair,fusion, resection, biopsy, or radiation treatment. Therefore, atechnique is needed whereby registration can be performed between thebody parts as depicted pre-procedurally on scans and the position andshape of these same body parts as detected intra-procedurally. Thistechnique must take into account that movement can occur betweenportions of the body which are not rigidly joined, such as bonesconnected by a joint, or fragments of a broken bone, and that shapedeformation can occur for semi-rigid bodies, such as the liver orprostate. In particular, the technique must be able to modify thescanned image dataset such that the modified image dataset which is usedfor localization and display, corresponds to position and/or shape ofthe body part(s) of interest during a medical or surgical procedure. Akey to achieving this correspondence is the ability to precisely detectand track the position and/or shape of the body part(s) of interestduring the medical or surgical procedure, as well as to trackinstruments, or radiation used during the said procedure.

SUMMARY OF THE INVENTION

[0008] It is an object of this invention to provide a system whichallows registration between a body part depicted in pre-proceduralimages and tracked during surgery.

[0009] It is a further object of this invention to provide a systemwhich allows registration between a semi-rigid body such as the liverdepicted in pre-procedural images and detected during surgery.

[0010] It is a further object of this invention to provide a systemwhich allows registration between multiple body parts such as skeletalelements depicted in pre-procedural images and detected during surgery.

[0011] It is a further object of this invention to provide a systemwhich can localize a semi-rigid body that may deform between imaging anda procedure and provide a display during the procedure of the body inits deformed shape.

[0012] It is a further object of this invention to provide a systemwhich can localize multiple rigid bodies that move with respect to eachother between imaging and a procedure and provide a display during theprocedure of the bodies in their displaced positions.

[0013] It is another object of this invention to provide a system foruse during a medical or surgical procedure on the body, the systemgenerating a display representing the position of one or more bodyelements during the procedure based on a scan generated by a scannereither prior to or during the procedure.

[0014] It is another object of this invention to provide a system foruse during a medical or surgical procedure on a body which modifies thescan taken prior to or during a procedure according to the identifiedrelative position of each of the elements during the procedure.

[0015] It is another object of this invention to provide a system foruse during a medical or surgical procedure on a body which modifies theimage data set according to the identified shape of each of the elementduring the procedure.

[0016] It is another object of this invention to provide a system whichgenerates a display representative of the position of a medical orsurgical instrument in relation to the body element(s) during aprocedure.

[0017] It is a further object of this invention to provide a system foruse during image guided medical and surgical procedures which is easilyemployed by the doctor or surgeon conducting the procedure.

[0018] It is another object of this invention to provide a system whichdetermines the relative position and/or shape of body elements during amedical or surgical procedure based on the contour of the body elementswhich can avoid the need for exposing the body elements.

[0019] It is still another object of this invention to provide a systemwhich employs one or more two dimensional fluoroscopic or x-ray imagesof body elements to determine their relative position and/or shape inthree dimensions.

[0020] It is yet a further object of this invention to describe asurgical or medical procedure which employs a display representing theposition of the body element(s) during the procedure based on an imagedata set of the body element(s) generated prior to the procedure.

[0021] It is a further object of this invention to provide a system andmethod for medical or surgical procedures which allows repositioning ofbody elements during the procedure and still permits the generation of aimage showing the relative position of the body elements.

[0022] It is a further object of this invention to provide a system andmethod for medical or surgical procedures which allows reshaping of thebody element(s) during the procedure and still permits the generation ofa image showing the position and current shape of the body elements.

[0023] It is a further object of this invention to provide a systemwhich can localize a body element and provide a display during theprocedure of the position of the body element relative to an instrument,such as a forceps, microscope, or laser, so that the instrument can beprecisely located relative to the body element.

[0024] Other objects and features will be in part apparent and in partpointed out hereinafter.

[0025] The invention comprises a system for use during a medical orsurgical procedure on a patient's body. The system generates one or moreimages representing the position and shape of one or more body elementsduring the procedure using scans generated by a scanner prior to theprocedure, the scans having at least one reference point for each of thebody elements of interest. These two dimensional scans, taken together,comprise a three dimensional depiction of the body, and are called theimage data set. The reference points of a particular body element have aspatial relation to the particular body element. The system includesmeans for identifying, during the surgical or medical procedure, theposition of the reference points of each of the body elements to bedisplayed by the system. The system also includes a means processor formodifying the image data set according to the identified position of thereference points of each of the body elements during the medical orsurgical procedure, called the identifying means. The processorgenerates images using a modified (displaced and/or deformed) image dataset representing the position and shape of the body elements during theprocedure. Optionally, the processor determines the position of amedical or surgical instrument relative to these body elements. Thesystem also includes a display which utilizes the modified image dataset generated by the processor to illustrate the position and shape ofthe body elements during the procedure and optionally the determinedposition of the medical or surgical instrument relative to the bodyelements by means of two dimensional images.

[0026] The invention also comprises a method for use during a procedure.The method generates images representing the position and shape of oneor more body elements during the procedure based on scans generatedprior to the procedure, which scan set has reference points for each ofthe body elements. The method comprises the steps of:

[0027] identifying, during the procedure, the position of the referencepoints of each of the body elements to be displayed;

[0028] modifying the image data set according to the identified positionof the reference points of each body element during the procedure inorder to generate a modified (displaced and/or deformed) image data setrepresenting the position of the body elements during the procedure;

[0029] optionally determining the position of a medical or surgicalinstrument, probe or beam of irradiation relative to the body elements;and

[0030] generating a display based on the modified image data setillustrating the position and shape of the body elements during theprocedure and optionally the position of the medical or surgicalinstrument relative to the body elements.

[0031] The invention also comprises a method for use with two or morebody elements each of which have reference points. Prior to theprocedure, the method comprises the steps of placing the body elementsin a frame to fix their relative position; and scanning the fixed bodyelements. During the procedure, the method comprises the steps of:

[0032] placing the body elements in the frame so that the body elementshave the same relative position as their position during scanning;

[0033] determining the position of reference points on the body elementsrelative to reference means;

[0034] determining the position of a medical or surgical instrumentrelative to the reference means;

[0035] determining the position of the medical or surgical instrumentrelative to the body elements; and

[0036] generating a display based on the pre-procedural scanningillustrating the determined position of the medical or surgicalinstrument relative to the body elements.

[0037] The invention also comprises a device for use with a surgicalnavigation system having a sensor array which is in communication withthe device to identify its position, the device for use in guiding acatheter, the device for engaging a cable connected to the surgicalnavigation system, the cable for providing signals for activating thedevice. A handle has a cavity therein. A plurality of light emittingdiodes on the handle emit light, when activated, for communicating withthe sensor array of the surgical navigation system. A connector attachedto the handle and adapted to engage the cable connected to the surgicalnavigation system receives the signals for activating the diodes. Wireslocated in the cavity of the handle and electrically interconnecting theconnector and the light emitting diodes transmit the signals received bythe connector to the diodes. A guide member connected to the handleguides the catheter.

[0038] The invention also comprises a device for use with a surgicalnavigation system having a sensor array which is in communication withthe device to identify its position. A base member has a cavity therein.A plurality of light emitting diodes on the base member emit light, whenactivated, for communicating with the sensor array of the surgicalnavigation system. An activating circuit connected to the diodesprovides signals for activating the diodes. Wires located in the cavityof the base member and electrically interconnecting the power supply andthe light emitting diodes transmit the signals for activating thediodes.

[0039] The invention also comprises a device for use with a surgicalnavigation system having a sensor array which is in communication withthe device to identify its position, the device for engaging a structureattached to or an instrument in known relation to a body part therebyproviding a known reference relative to the body part, the device havinga connector for engaging a cable connected to the surgical navigationsystem, the cable for providing signals for activating the device. Abase member has a cavity therein. A coupling on the base member engagesthe structure in order to maintain the base member in fixed relation tothe body part thereby providing the fixed reference. A plurality oflight emitting diodes on the base member, said diodes, when activated,emitting light for communicating with the sensor array of the surgicalnavigation system. A connector attached to the base member and adaptedto engage the cable connected to the surgical navigation system receivesthe signals for activating the diodes. Wires located in the cavity ofthe base member and electrically interconnecting the connector and thelight emitting diodes transmit the signals received by the connector tothe diodes to activate the diodes.

[0040] The invention also comprises a device for use with a surgicalnavigation system having a sensor array which is in communication withthe device to identify its position, the device for guiding aninstrument for engaging a body part thereby locating the instrument at aknown position relative to the body part, the device having a connectorfor engaging a cable connected to the surgical navigation system, thecable for providing signals for activating the device. A housing has acavity therein. A structure on the housing guides the instrument inorder to maintain the instrument in a relationship relative to thehousing. A plurality of light emitting diodes on the housing, whenactivated, emit light for communicating with the sensor array of thesurgical navigation system. A connector attached to the housing andadapted to engage the cable connected to the surgical navigation systemreceives the signals for activating the diodes. Wires located in thecavity of the housing and electrically interconnecting the connector andthe light emitting diodes and for transmitting the signals received bythe connector to the diodes to activate the diodes.

[0041] In addition, the invention comprises a surgical navigation systemcomprising:

[0042] a controller;

[0043] a sensor array;

[0044] a reference frame in communication with the array to identify itsposition; and

[0045] a localization frame in communication with the array to identifya position of the localization frame, the localization frame for guidingthe instrument for engaging the body part thereby locating theinstrument at a known position relative to the body part, thelocalization frame connected to the controller which provides signalsfor activating the localization frame.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is an illustration of the prior art system in which rigidfixation and absence of movement between imaging and surgery permits aone-to-one registration process between the pre-surgical scan and theposition in surgery.

[0047]FIG. 2A is an illustration of operation of the invention in whichthe pre-procedural image data set is modified in accordance with theintra-procedural position in order to generate a displaced and/ordeformed data set representative of the intra-procedural position.

[0048]FIG. 2B is a block diagram of one preferred embodiment of a systemaccording to the invention.

[0049]FIG. 3 is an illustration of the pre-procedural alignment of threebody elements during scanning.

[0050]FIG. 4 is an illustration of the intra-procedural alignment of thethree body elements of FIG. 3 during surgery.

[0051]FIG. 5 is an illustration of three body elements, one of which hasa reference frame attached thereto, in combination with a registrationprobe.

[0052]FIG. 6 is an illustration showing ultrasound registrationaccording to the invention in which emitters are attached to theultrasound for a virtual reference and, optionally, the patient's bodyfor an actual reference.

[0053]FIG. 7 is an illustration of a fluoroscopic localizer according tothe invention for providing projections of an image of the bodyelements.

[0054]FIG. 8 is an illustration of a drill guide instrument of theinvention wherein the position of a drill guide relative to the bodyelements may be displayed.

[0055]FIGS. 9 and 10 illustrate a clamped reference frame and a wiredreference frame, respectively.

[0056]FIG. 11 is a schematic diagram of one preferred embodiment of acranial surgical navigation system according to the invention.

[0057]FIG. 11A is a top plan view of one preferred embodiment of acranial reference arc frame according to the invention.

[0058]FIG. 11B is a side plan view, partially in cross section, of onepreferred embodiment of a cranial reference arc frame according to theinvention.

[0059]FIG. 11C is a wiring diagram of one preferred embodiment of acranial reference arc frame according to the invention.

[0060]FIG. 12A is a top plan view of one preferred embodiment of aspinal reference arc frame according to the invention.

[0061]FIG. 12B is a front plan view, partially in cross section, of onepreferred embodiment of a spinal reference arc frame according to theinvention.

[0062]FIG. 12C is a side plan view of one preferred embodiment of aspinal reference arc frame according to the invention.

[0063]FIG. 12D is a top plan view of one preferred embodiment of athoraco-lumbar mount according to the invention.

[0064]FIG. 12E is a front plan view, partially in cross section, of onepreferred embodiment of a thoraco-lumbar mount according to theinvention.

[0065]FIG. 12F is a side plan view of one preferred embodiment of athoraco-lumbar mount according to the invention.

[0066]FIG. 12G is a wiring diagram of one preferred embodiment of aspinal reference arc frame according to the invention.

[0067]FIG. 13A is a top plan view of one preferred embodiment of abiopsy guide localization frame according to the invention.

[0068]FIG. 13B is a side plan view, partially in cross section, of onepreferred embodiment of a biopsy guide localization frame according tothe invention.

[0069]FIG. 13C is a front plan view of one preferred embodiment of abiopsy guide localization frame according to the invention.

[0070]FIG. 13D is a top plan view of one preferred embodiment of a drillguide localization frame according to the invention.

[0071]FIG. 13E is a side plan view, partially in cross section, of onepreferred embodiment of a drill guide localization frame according tothe invention.

[0072]FIG. 13F is a top plan view of one preferred embodiment of a drillyoke localization frame according to the invention.

[0073]FIG. 13G is a side plan view, partially in cross section, of onepreferred embodiment of a drill yoke localization frame according to theinvention.

[0074]FIG. 13H is a top plan view of one preferred embodiment of aventriculostomy probe including an integrated localization frameaccording to the invention.

[0075]FIG. 13I is a side plan view, partially in cross section, of onepreferred embodiment of a ventriculostomy probe including an integrallocalization frame according to the invention.

[0076]FIG. 13J is a wiring diagram of one preferred embodiment of alocalization frame according to the invention.

[0077] Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Referring to FIG. 2, an overview of operation of one preferredembodiment of the system according to the invention is illustrated.Prior to a particular procedure, the body elements which will be part ofthe procedure are scanned to determine their alignment, i.e., theirpre-operative position. For example, the alignment may be such asillustrated in FIG. 3 wherein body elements 10, 20, and 30 are more orless aligned in parallel. These body elements may be bones or otherrigid bodies. In FIG. 3, three-dimensional skeletal elements 10, 20, 30are depicted in two dimensions as highly stylized vertebral bodies, withsquare vertebra 11, 21, 31, small rectangular pedicles 12, 22, 32, andtriangular spinous processes 13, 23, 33. During imaging, scans are takenat intervals through the body parts 10, 20, 30 as represented in. FIG. 3by nine straight lines generally referred to be reference character 40.At least one scan must be obtained through each of the body elements andthe scans taken together constitute a three-dimensional pre-proceduralimage data set.

[0079]FIG. 2B is a block diagram of the system according to theinvention. A scanner interface 102 allows a processor 104 to obtain thepre-procedural image data set generated by the scanner and store thedata set in pre-procedural image data set memory 106. Preferably, afterimaging, processor 104 applies a discrimination process to thepre-procedural image data set so that only the body elements 10, 20, 30remain in memory 106. If a discrimination process is employed, processor104 may execute the discrimination process while data is beingtransferred from the scanner through the scanner interface 102 forstorage in memory 106. Alternatively, memory 106 may be used for storingundiscriminated data and a separate memory (not shown) may be providedfor storing the discriminated data. In this alternative, processor 104would transfer the data set from the scanner through scanner interface102 into memory 106 and then would discriminate the data stored inmemory 106 to generate a discriminated image data set which would bestored in the separate memory.

[0080] Once the body elements 10, 20, 30 are discriminated and eachdefined as a single rigid body, they can be repositioned by establishedsoftware algorithms to form the displaced image data set. Each rigidbody element, 10, 20, 30, must have at least three recognizablereference points which are visible on the pre-procedural images. Thesereference points must be accurately detected during the procedure. Forbody part 10, reference points 10A, 10B, and 10C are located on thespinous process 13; for body part 20, reference points 20A and 20C arelocated on the vertebra 21 and reference point 20B is located on spinousprocess 23; and for body part 30, reference points 30A and 30B arelocated on the spinous process 33 and reference point 30C is located onthe vertebra 31. More than one reference point can be selected on eachscan through the bone, although the maximal accuracy of registration isachieved by separating the reference points as far as possible. Forexample, in the case of posterior spinal surgery, it may be preferableto select reference points 10A, 10B, and 10C on the spinous processwhich is routinely exposed during such surgery. It is contemplated thatsystem software may allow the manual or automated identification ofthese same points on the images of the body elements 10, 20, 30. As FIG.3 is a two-dimensional projection of a three-dimension process, thereference points will not be limited to a perfect sagittal plane, asdepicted.

[0081] After imaging, the skeletal body elements 10, 20, 30 may movewith respect to each other at the joints or fracture lines. In theprocedure room, such as an operating room or a room where a medicalprocedure will be performed, after positioning the patient the surgery,the body elements will assume a different geometry, such as the geometrydepicted in FIG. 4.

[0082] As a result of this movement, the pre-procedural image data setstored in memory 106, consisting of the scans through the skeletalelements, does not depict the operative position of the skeletalelements, as shown in FIG. 4. However, the shape of the skeletalelements, as depicted by the scans through the element, is consistentbetween imaging and procedure since they are rigid bodies, as indicatedby the lines 40 through each element in FIG. 4. Therefore, the imagedata set must be modified to depict the intraprocedural geometry of theskeletal elements. This modification is performed by identifying thelocation of each reference point of each skeletal element in procedurespace. As diagrammatically illustrated in FIG. 2, a localizer 108 (seeFIG. 13, below, for more details) identifies the location and providesthis information so that the pre-procedural data set may be deformed orre-positioned into the displaced data set. As a result, the displaceddata set is in registration with the intra-procedural position of theelements 10, 20, 30. Once the locations of the reference points aredetermined by the localizer 108, processor 104, which is a part of thework station, can execute software which re-positions the images of theskeletal elements to reflect the position of the actual elements in theprocedure room thus forming the displaced set and the registrationbetween the displaced set and the intra-procedural position.

[0083] Preferably, a three-dimensional digitizer may be used as thelocalizer 108 to determine the position and space of the elements 10,20, 30 during the procedure. In general, the digitizer would include areference array 110 which receives emissions from a series of emitters.Usually, the emissions consist of some sort of energy, such as light,sound or electromagnetic radiation. The reference array 110 is distantfrom the emitters which are applied to and positioned in coordinationwith the elements being localized, determining the position of theemitters. As is apparent, the emitters may be placed distant to theelements and the reference array 110 may be attached to the elementsbeing localized.

[0084] Referring to FIG. 2, an alternate preferred embodiment of thesystem according to the invention in the case where the body elementsare not rigid, but rather semi-rigid such that shape deformations mayoccur to the body elements is described as follows. Prior to aparticular procedure, the body elements which will be part of theprocedure are scanned to determine their pre-operative position andshape. For example, the alignment may be such as illustrated in FIG. 3wherein body elements 10, 20, and 30 are more or less aligned inparallel and have a defined shape. These body elements may be softtissue such as the prostate or other semi-rigid bodies.

[0085] After imaging, the elements 10, 20, 30 may move with respect toeach other and also their shape may become deformed. In the procedureroom, such as an operating room or a room where a medical procedure willbe performed, after positioning the patient the surgery, the bodyelements may assume a different geometry, such as the geometry depictedin FIG. 4 where geometry depicts both element alignment (position) andshape.

[0086] As a result of this changed geometry, the pre-procedural imagedata set stored in memory 106, does not depict the operative geometry ofthe body elements, as shown in FIG. 4. Indeed, the shape of the bodyelements, as depicted by the scans through the element, may have changedbetween imaging and procedure since they are semi-rigid bodies.Therefore, the image data set must be modified to depict the currentgeometry of the body elements. This modification is performed byidentifying the location of the reference points of each body element inprocedure space. As diagrammatically illustrated in FIG. 2, a localizer108 possibly in communication with a processor 104 identifies thelocation of the reference points and provides this information so thatthe pre-procedural data set may be deformed into the displaced data set.Once the locations of the reference points are determined, processor104, which is a part of the work station, can execute software whichmodifies the images of the body elements to reflect the geometry of theactual elements in the procedure room thus forming the displaced set andthe registration between the displaced set and the intra-proceduralposition. As a result, the displaced data set is in registration withthe intra-procedural geometry of the elements 10, 20, 30.

[0087] According to one preferred embodiment of the invention, areference frame 116 is attached to one of the body elements 10 at thebeginning of the procedure. Various reference frame embodiments areillustrated in more detail in FIGS. 11 and 12, below. Reference frame116 is equipped with a plurality of emitters 114 which together define athree-dimensional intraprocedural coordinate system with respect to thebody element 10. In conventional terms, the reference frame 116 definesthe stereotactic space with respect to the body element 10. Emitters 114communicate with sensors 112 on a reference array 110 located in theprocedure room and remote from the reference frame 116 and patient. Ifthe body of the patient is not immobilized during surgery, then multiplereference frames may be required for each body element to define asurgical space with respect to each element. The surgical space mayalternatively be defined by rigid fixation of the frame emitters 114directly (or indirectly, for example; to the skin) to the skeletalelements 10, 20, or 30. In either case, the emitters 114 emit a signalwhich is received by the sensors 112. The received signal is digitizedto compute position, for example, by triangulation. Through suchinformation, the localizer 108 or a digitizer which is part of thelocalizer 108 can determine the exact three-dimensional position of theframe emitters 114 relative to the sensors 112. Thereby, localizer 108or the processor 104 can exactly determine the position of the referenceframe 116 relative to the array which is free to move except duringlocalization, e.g., activation of the emitters 114 on the referenceframe 116 and activation of the probe emitters 112. Emitters 114 of thereference frame 116 are energized to provide radiation to the sensors112, which radiation is received and generates signals provided to thelocalizer 108 for determining the position of the frame 116 relative tothe array 110.

[0088] Next, it is necessary to determine the position of the bodyelement 10, which may be a skeletal element, to which the referenceframe 116 is affixed or positioned with respect to. In particular, theposition of the body element 10 relative to the reference frame 116 mustbe determined, thereby determining the position of the body element 10in the surgical space defined by the reference frame 116. After exposureof the reference points 10A, 10B, 10C by surgical dissection, thereference points are touched by the tip of a registration probe 118equipped with emitters 120. As each of the reference points 10A, 10B,10C is touched by the tip of the probe 120, the emitters are energizedto communicate with the sensors 112 of reference array 110. Thiscommunication permits the localizer 108 to determine the position of theregistration probe 120, thereby determining the position of the tip ofthe probe 120, thereby determining the position of the reference point10A on which the tip is positioned. By touching each of the referencepoints 10A, 10B, 10C on each body element 10, 20, 30 involved in theprocedure, an intra-procedural geometry data is generated and stored inmemory 121. This data is related to the corresponding reference pointson the pre-procedural images of the same elements by processor 104 whichemploys software to derive a transformation which allows thedetermination of the exact procedural position, orientation, and shapein surgical space of each body element, and thereby modifies thepre-procedural image data set stored in memory 106 to produce adisplaced image data set which is stored in memory 122. The displacedimage data set in memory 122 reflects the geometry of the actualelements 10, 20, 30 during the procedure. Processor 104 displays thedisplaced image data set on display 124 to provide a visual depiction ofthe geometry of the body elements 10, 20, 30 during the procedure. Thisimage is used during the procedure to assist in the procedure. Inaddition, it is contemplated that an instrument, such as a forceps, alaser, a microscope, a endoscope, or a radiation delivery system, whichwould be used during the procedure may be modified by the addition ofemitters. This modified device when moved into the area of the bodyelements 10, 20, 30 would be activated so that its emitters wouldcommunicate with the reference array 110 thereby permitting localizer108 to determine the instrument's position. As a result, processor 104would modify display 124 to indicate the position of the instrument orthe instruments focal point, such as by positioning a cursor, withrespect to the body elements 10, 20, 30.

[0089] Further, it is contemplated that the addition of emitters on aninstrument (effector) may be used with the system in order to create aclosed-loop feedback for actively (in the case of robotics) or passivelycontrolling or monitoring the instrument and its position. Such acontrol loop allows the monitoring of certain procedures such as thedelivery of radiation to the body or the use of a drill where the objectof the procedure is to keep the focal point of the instrument in a safezone, i.e. a predetermined procedural plan. Such a control loop couldalso control the operation of a robotically controlled instrument wherethe robotics could be driven (directly or indirectly) by processor 104to control the position the position of the instrument. For example, theprocessor could instruct a robotic arm to control the position of alaser. The laser position could be monitored, such as by emitters on thelaser. The processor would be programmed with the control parameters forthe laser so that it would precisely follow a predetermined path.

[0090] Reference frame 116 allows the patient to be moved during theprocedure without the need for re-registering the position of each ofthe body elements 10, 20, 30. It is assumed that during the procedure,the body elements are fixed relative to each other. Since the referenceframe 116 is fixed (directly or indirectly) to body element 10, movementof the patient results in corresponding movement of the reference frame116. Periodically, or after each movement of the patient, array emitters114 may be energized to communicate with the sensors 112 of referencearray 110 in order to permit localizer 108 to determine the position ofthe reference frame 116. Since the reference frame 116 is in a knownrelative position to element 110 and since we have assumed that elements20 and 30 are in fixed relation to element 10, localizer 108 and/orprocessor 104 can determine the position of the elements and therebymaintain registration.

[0091] An alternative to touching the reference points A, B, C with thetip of the probe 118 would be to use a contour scanner 126 a withemitters attached 126 b. Such a device, using some form of energy suchas sound or light which is emitted, reflected by the contour and sensed,would allow the extraction of a contour of the body elements 10, 20, 30,thus serving as a multitude of reference points which would allowregistration to occur. The registration process is analogous to theprocess described for ultrasound extracted contours below.

[0092] In certain situations, markers may be used on the skin surface asreference points to allow the transformation of the pre-procedural imagedata set into the displaced image data set. Reciprocally, skin surfacefiducials applied at the time of imaging can be used to re-position thebody to match the geometry during imaging and is described below.

[0093] Localization of body elements 10, 20, 30 may be desired withoutintra-procedural exposure of the reference points A, B, C on those bodyelements. Examples wherein the spine is minimally exposed includepercutaneous biopsy of the spine or discectomy, spinal fixation,endoscopy, percutaneous spinal implant insertion, percutaneous fusion,insertion of drug delivery systems, and radiation delivery. In thissituation, localization of reference points on the body elements must bedetermined by some form of imaging which can localize through overlyingsoft tissue and/or discriminate surrounding tissue and structures. Thereare currently two imaging techniques which are available to a surgeon inthe operating room or a doctor in a procedure room which satisfy theneeds of being low cost and portable. Both imaging techniques,ultrasonography and radiography, can produce two- or three-dimensionalimages which can be employed in the fashion described herein to registera three-dimensional form such as a skeletal element.

[0094] As described in U.S. patent application Ser. Nos. 07/858,980 and08/053,076, the entire disclosures of which are incorporated herein byreference, the coupling of a three-dimensional digitizer to a probe ofan ultrasound device affords benefits in that a contour can be obtainedwhich can be related directly to a reference system that definesthree-dimensional coordinates in the procedural work space, i.e., thesurgical space. In the context of the present invention, a patient isimaged prior to a procedure to generate a pre-procedural image data setwhich is stored in memory 106. In the procedure room, the patient's bodyis immobilized to stabilize the spatial relationship between the bodyelements 10, 20, 30. A procedural reference system, surgical space, forthe body is established by attaching a reference frame 116 to one of thebody elements or by otherwise attaching emitters to the patient or bodyelements as noted above, or by attaching emitters to a device capable oftracking one of the body elements thereby forming a known relationshipwith the body element. For example, this could be performed by using thepercutaneous placement of a reference frame similar to the one describedabove, radiopaque markers screwed into the elements or by placingemitters 130 directly on the skins, as illustrated in FIG. 6, based onthe assumption that the skin does not move appreciably during theprocedure or in respect to the body elements.

[0095] An ultrasound probe 128 equipped with at least three emitters 130is then placed over the body element of interest. The contour (which canbe either two- or three-dimensional) of the body element is thanobtained using the ultrasound probe 128. This contour can be expresseddirectly or indirectly in the procedural coordinates defined by thereference system (surgical space). Emitters 130 communicate with sensors112 of reference array 110 to indicate the position of the ultrasoundprobe 128. An ultrasound scanner 130 which energizes probe 128determines the contour of the body element of interest and beingscanned. This contour information is provided to processor 104 forstorage in intra-procedural geometry data memory 121.

[0096] The intra-procedural contour stored in memory 121 is thencompared by a contour matching algorithm to a corresponding contourextracted from the pre-operative image data set stored in memory 106.Alternatively, a pre-procedural contour data set may be stored in memory134 based on a pre-procedural ultrasound scan which is input into memory134 via scanner interface 102 prior to the procedure. This comparisonprocess continues until a match is found for each one of the elements.Through this contour matching process, a registration is obtainedbetween the images of each body element and the corresponding positionof each element in the procedural space, thereby allowing the formationof the displaced image data set 122 used for localization and display.Note that the contours used in the matching process only have to besufficiently identical to accomplish a precise match—the contours do nothave to be the same extent of the body element.

[0097] In certain instances, the ultrasound registration noted above maynot be applicable. For example, ultrasound does not penetrate bone, andthe presence of overlying bone would preclude the registration of anunderlying skeletal element. Further, the resolution of ultrasounddeclines as the depth of the tissue being imaged increases and may notbe useful when the skeletal element is so deep as to preclude obtainingan accurate ultrasonically generated contour. In these circumstances, aradiological method is indicated, which utilizes the greater penetratingpower of x-rays.

[0098] Pre-operative imaging occurs as usual and the skeletal elementsmay be discriminated from the soft tissue in the image data set asabove. In particular, a CT scan of the skeletal elements 10, 20, 30could be taken prior to the procedure. Processor 104 may thendiscriminate the skeletal elements and store the pre-procedural imagedata set in memory 106. Next, the patient is immobilized for theprocedure. A radiograph of the skeletal anatomy of interest is taken bya radiographic device equipped with emitters detectible by thedigitizer. For example, a fluoroscopic localizer 136 is illustrated inFIG. 7. Localizer 136 includes a device which emits x-rays such as tube138 and a screen 140 which is sensitive to x-rays, producing an imagewhen x-rays pass through it. This screen is referred to as afluoroscopic plate. Emitters 142 may be positioned on the tube 138, oron the fluoroscopic plate 140 or on both. For devices in which the tube138 is rigidly attached to the plate 140, emitters need only be providedon either the tube or the plate. Alternatively, the reference array 110may be attached to the tube or the plate, obviating the need foremitters on this element. By passing x-rays through the skeletal element141 of interest, a two-dimensional image based on bone density isproduced and recorded by the plate. The image produced by thefluoroscopic localizer 136 is determined by the angle of the tube 138with respect to the plate 140 and the position of the skeletal elementstherebetween and can be defined with respect to procedure coordinates(surgical space). Fluoroscopic localizer 136 includes a processor whichdigitizes the image on the plate 140 and provides the digitized image toprocessor 104 for possible procesing and subsequent storage inintra-procedural geometry data memory 121. Processor 104 may simulatethe generation of this two-dimensional x-ray image by creating a seriesof two-dimensional projection of the three-dimensional skeletal elementsthat have been discriminated in the image data set stored in memory 106.Each two dimensional projection would represent the passage of an X-raybeam through the body at a specific angle and distance. In order to formthe displaced data set and thus achieve registration, an iterativeprocess is used which selects that a two-dimensional projection throughthe displaced data set that most closely matches the actual radiographicimage(s) stored in memory 121. The described process can utilize morethan one radiographic image. Since the processor 104 is also aware ofthe position of the fluoroscopic localizers because of the emitters 142thereon, which are in communication with localizer 108, the exactposition of the skeletal elements during the procedure is determined.

[0099] As noted above, the procedural reference system or surgical spacefor the body can be established by attaching emitters to a devicecapable of detecting and tracking, i.e. identifying, one of the bodyelements thereby forming a known relationship with the body element. Forexample, the emitters 130 on the ultrasound probe 128 together andwithout the three emitters on the patient's body form a type ofreference frame 116 as depicted in FIG. 6 which can be virtuallyattached to body element 10 by continuously or periodically updating theultrasound contour of body element 10 stored in intra-proceduralgeometry data memory 121 which the processor 104 then uses to match tothe contour of body element 10 stored in pre-procedural memory 106thereby continuously or periodically updating the displaced image dataset in memory 122 so that registration with the procedural position ofthe body elements is maintained. It is contemplated that a virtualreference frame can be accomplished using any number of devices that arecapable of detecting and tracking a body element such as radiographicdevices (fluoroscope), endoscopes, or contour scanners.

[0100] The above solutions achieve registration by the formation of adisplaced image data set stored in memory 122 which matches thedisplacement of the skeletal elements at the time of the procedure. Analternative technique to achieve registration is to ensure that thepositions of the skeletal elements during the procedure are identical tothat found at the time of imaging. This can be achieved by using a framethat adjusts and immobilizes the patient's position. In this technique,at least three markers are placed on the skin prior to imaging. Thesemarkers have to be detectible by the imaging technique employed and arecalled fiducials. A multiplicity of fiducials is desirable for improvingaccuracy.

[0101] During the procedure, the patient's body is placed on a framethat allows precise positioning. Such frames are commonly used forspinal surgery and could be modified to allow their use during imagingand could be used for repositioning the patient during the procedure.These frames could be equipped with drive mechanisms that allow the bodyto be moved slowly through a variety of positions. The fiducials placedat the time of imaging are replaced by emitters. By activating the drivemechanism on the frame, the exact position of the emitters can bedetermined during the procedure and compared to the position of thefiducials on the pre-procedural image data set stored in memory 106.Once the emitters assume a geometry identical to the geometry of thefiducials of the image data set, it is considered that the skeletalelements will have resumed a geometric relationship identical to theposition during the pre-procedural scan, and the procedure can beperformed using the unaltered image data set stored in memory 106.

[0102] In general, instrumentation employed during procedures on theskeleton is somewhat different than that used for cranial applications.Rather than being concerned with the current location, surgery on theskeleton usually consists of placing hardware through bones, taking abiopsy through the bone, or removing fragments. Therefore, theinstrumentation has to be specialized for this application.

[0103] One instrument that is used commonly is a drill. By placingemitters on a surgical drill, and by having a fixed relationship betweenthe drill body and its tip (usually a drill bit), the direction andposition of the drill bit can be determined. At least three emitterswould be needed on the drill, as most drills have a complexthree-dimensional shape. Alternatively, emitters could be placed on adrill guide tube 800 having emitters 802, and the direction 804 of thescrew being placed or hole being made could be determined by thedigitizer and indicated on the image data set (see FIG. 8). The skeletalelement 806 would also have emitters thereon to indicate its position.

[0104] Besides modification of existing instrumentation, newinstrumentation is required to provide a reference system for surgery asdiscussed above. These reference frames, each equipped with at least 3emitters, require fixation to the bone which prevents movement orrotation.

[0105] For open surgery, a clamp like arrangement, as depicted in FIG.9, can be used. A clamp 900 is equipped with at least two points 902,904, 906, 908 which provide fixation to a projection 910 of a skeletalelement. By using at least two point fixation the clamp 900, whichfunctions as a reference frame, will not rotate with respect to theskeletal element. The clamp includes emitters 912, 914, 916 whichcommunicate with the array to indicate the position of the skeletalelement as it is moved during the procedure.

[0106] Many procedures deal with bone fragments 940 which are notexposed during surgery, but simply fixated with either wires or screws950, 952 introduced through the skin 954. FIG. 10 depicts a referenceplatform 956 attached to such wires or screws 950, 952 projectingthrough the skin 954. The platform 956 includes a plurality of emitters958, 960, 962, 964 which communicate with the array to indicate theposition of the bone fragment 940 as it is moved during the procedure.

[0107] The reference frame can be slipped over or attached to theprojecting screws or wires to establish a reference system.Alternatively, the frame can be attached to only one wire, as long asthe method of attachment of the frame to the screw or wire preventsrotation, and that the wire or screw cannot rotate within the attachedskeletal element.

REFERENCE AND LOCALIZATION FRAMES

[0108]FIG. 11 is a schematic diagram of one preferred embodiment of acranial surgical navigation system according to the invention. Portablesystem cabinet 102 includes a surgical work station 104 which issupported for viewing by the surgeon or technician using the system.Work station 104 includes a screen 106 for illustrating the variousscans and is connected to a personal computer 108 for controlling themonitor 106. The system also includes an optical digitizer including acamera array 110, a camera mounting stand 112 for supporting the arrayremote from and in line of sight with the patient, a digitizer controlunit 114 on the portable system cabinet 102 and connected to thecomputer 108, a foot switch 116 for controlling operation of the systemand a breakout box 118 for interconnecting the foot switch 116 and thedigitizer control unit 114.

[0109] Also connected via the break out box 118 is a reference frameassembly 120 including a reference frame 122 with cable connected to thebreak out box 118, a vertical support assembly 124, a head clampattachment 126 and a horizontal support assembly 128. Optical probe 130(which is a localization frame) is also connected via cable to thedigitizer control unit 114 via the break out box 118.

[0110] In operation, a patient's head (or other “rigid” body element) isaffixed to the head clamp attachment 126. To determine the position ofoptical probe 130 with respect to the head within the head clampattachment 126, a surgeon would step on pedal 116 to energize theemitters of reference frame 122. The emitters would generate a lightsignal which would be picked up by camera array 110 and triangulated todetermine the position of the head. The emitters of the optical probe130 would also be energized to emit light signals which are picked up bythe camera array to determine the position of the optical probe 130.Based on the relative position of the head and the probe 130, controlbox 114 would illustrate a preoperative scan on the screen of monitor106 which would indicate the position of the probe relative to and/orwithin the head.

[0111]FIG. 11A is a top plan view of one preferred embodiment of acranial reference arc frame 122 according to the invention. Referenceframe 122 is for use with a surgical navigation system such asillustrated in FIG. 11 having a sensor array such as camera array 110which is in communication with the reference frame 122 to identify itsposition. The reference frame 122 includes a base member 132 having anupper base 134 and a base plate 136 which each have a semi-circularconfiguration and are joined together by screws 138 to form a cavity 140therebetween. The base and plate may be made of anodized aluminum orother autoclavable material. The top of the upper base may be providedwith one or more spring clamps 142 for engaging a Leyla retractor arm.As shown in FIG. 11A, the upper base is provided with five spring clamps142.

[0112] Either or both ends of the reference frame 122 may be providedwith a bayonet fitting 144 for engaging a clamp which would also engagea Leyla retractor. One or both ends of the reference frame 122 is alsoformed into a radial projection 146 for supporting a screw 148 and crankhandle 150 used to lock the reference frame to a head clamp such as headclamp 126 shown in FIG. 11 or a Mayfield clamp. This allows thereference frame 122 to be placed in a fixed position relative to thehead so that any movement of the head would also include correspondingmovement of the reference frame 122.

[0113] Radial projection 146, screw 148 and handle 150 constitute acoupling on the base member 132 for engaging a structure attached to abody part (the head) thereby providing a fixed reference relative to thehead in order to maintain the base member 132 in fixed relation to thehead.

[0114] Equally spaced about the reference frame 122 are a plurality ofLEDs 152 for communicating with the camera array 110. The LEDs 152 aremounted in holes 154 in the upper base 134, which holes 154 are incommunication with the cavity 140. Wires 156 are connected to each ofthe terminals of the LEDs 152 are positioned within the cavity 140. Theother ends of the wires are connected to a connector 158 for engaging acable connected to the digitizer 114 of the surgical navigation system.The cable provides signals for activating the LEDs 152. Connector 158 ismounted on a support projection 160 which projects from the base plate136. This support projection 160 has a channel therein for permittingthe wires to be connected to the connector 128. FIG. 11A is a wiringdiagram of one preferred embodiment of the reference frame 122 accordingto the invention. As is illustrated in Fig. 11C, each LED terminal isconnected to a separate pin of the connector 158. Although the inventionis illustrated as having a connector for engaging a cable, it iscontemplated that the reference frame 122 may be battery operated sothat no cable is necessary.

[0115] The reference frame 122 is essentially a semi-circular arc sothat it fits around the head of the patient to allow communication ofmultiple LEDs 152 on the reference frame 122 with the camera array 110.The multiple LEDs 152 on the reference frame 122 are positioned in aprecisely known geometric arrangement so that the calibration of thecamera array 110 can be checked continuously by comparing the LEDsgeometric positions as calculated by the digitizer 114 with thoseprecisely known geometric positions. Inconsistencies in this informationindicates the need to recalibrate the system or to reposition thereference frame 122 so that it can more accurately communicate with thecamera array 110. Frame 122 also includes a calibration divot 162. Inparticular, divot 162 is an exactly located depression within the upperbase 134 and is used to calibrate or check the calibration during themedical or surgical procedure the position of the tip of the probe. Theprecise location of each of the LEDs 152 relative to the calibrationdivot 162 is known. Therefore, locating a tip of a localization frameprobe in the calibration divot 162 allows the calibration or thecalibration check of the probes in the following manner. The tip of theprobe is located within the calibration divot 162 and the LEDs on theprobe are energized to provide light signals to the camera array 110.The LEDs on the reference frame 122 are also energized to communicatewith the camera array 110. Using the known position of the divot 162with respect to the position of each of the LEDs 152 as calculated bythe digitizer 114, the location of the calibration divot 162 is comparedto the location of the tip of the probe as calculated by the digitizerusing the LEDs on the probe in order to confirm that there is nodistortion in the probe tip relative to the divot 162. Distortion in theprobe tip indicates the need to recalibrate the probe so that it canmore accurately communicate with the camera array 110 or to retire theprobe.

[0116]FIGS. 12A, 12B, and 12C illustrate another preferred embodiment ofthe reference frame in the form of a spine reference arc frame 200. Aswith reference frame 122, spine reference arc frame 200 has an upperbase 202 which engages a base plate 204 to form a cavity 206therebetween. As shown in FIG. 12A, the spine reference arc frame 200has a generally U-shape configuration with LEDs 208 located at the endsof the legs 209 of the U-shaped member and at the intersection of thelegs and base 211 of the U-shaped member. Projecting laterally from thebase 211 is a coupling 210 for engaging a thoraco-lumbar mount 212 asillustrated in FIGS. 12D, 12E, and 12F. Also positioned on the base 211is a calibration divot 214 which is a depression having the same purposeas the calibration divot 162 of the reference frame 122. Coupling 210has twenty-four evenly spaced teeth 216 arranged in a circular patternfor engaging the twenty-four equally spaced teeth 218 of thethoraco-lumbar mount. This allows the spine reference arc frame 200 tobe positioned to form various angles relative to the mount 212. It iscontemplated that any other variable position connector may be used tojoin the spine reference arc frame 200 and the mount 212. Base plate 204has an opening therein for engaging a connector 220 for receiving acable to the digitizer control unit 114. The LEDs 208 are connected tothe connector 220 by wires 222 as illustrated in wiring diagram FIG.12G.

[0117] Referring to FIGS. 12D, 12E, and 12F, thoraco-lumbar mount 212comprises a clamp shaft 224 having an axial bore therein within which ispositioned an actuating shaft 226 which is connected to an actuatingknob 228 extending beyond the end of clamp shaft 224. The end of theactuating shaft 226 opposite the actuating knob 228 has an internalthreaded bore 230 which engages external threads of an actuation screw232. A U-shaped head 234 of screw 232 supports a pivot pin 236 betweenits legs. The pivot pin passes through the jaws 238 so that the jaws 238rotate about the pivot pin 236 and move relative to each other defininga receiving area 240 within which a spinal bone or other body part maybe clamped. The jaws 238 have teeth 239 for engaging a spinal bone orother body part and are spring loaded and held in their open position byspring plungers 242. As the actuating knob 228 is turned to engage thethreads of actuation screw 232, the screw 232 is drawn into the bore 230also drawing the jaws into a housing 246. This results in the cammingsurfaces 244 of housing 246 engaging the follower surfaces 248 of thejaws 238 closing the jaws and closing the receiving area 240 as the jawsare pulled into the housing.

[0118] The other end of clamp shaft 224 has a perpendicular projection250 for supporting the teeth 218 which engage the teeth 216 of thecoupling 210 of the spine reference arc frame 200. A spine reference arcclamp screw 252 passes through the array of teeth 218 and engages athreaded opening 254 in the coupling 210 of frame 200. Screw 252 engagesopening 254 and locks teeth 216 and teeth 218 together to fix the anglebetween the spine reference arc frame 200 and the thoraco-lumbar mount212. As a result, when the mount 212 is connected to a bone by placingthe bone in the receiving area 240 and turning the actuating knob 228 toclose the jaws 238 and the receiving area, the frame 200 is in a fixedposition relative to the bone which is engaged by the jaws. Any movementof the bone results in movement of the frame 200 which can be detectedby the camera array 110.

[0119] Referring to FIGS. 13A, 13B and 13C, one preferred embodiment ofa localization biopsy guide frame 300 is illustrated. In general, theframe 300 includes a localization frame 302 which supports a biopsyguide 304 and which also supports a support pin 306. The localizationframe 302 is comprised of an upper base 308 and a base plate 310 whichjoin to form a cavity 312 within which the wires 314 connecting to theLEDs 316 are located. As shown in the FIG. 13A, the localization framehas an elongated portion 318 and a generally V-shaped portion 320 havinglegs 322 and 324. An LED 316 is located at the end of each of the legs322 and an LED 316 is also located at the ends of the elongated portion318. As a result the four LEDs 316 form a rectangular array. However,the underlying localization frame 302 does not have a rectangularconfiguration which allows it to be adapted for other uses, such as adrill guide assembly as illustrated and described below with regard toFIGS. 13D and 13E. In general, the V-shaped portion 320 extendslaterally from the elongated portion 318 in order to accomplish therectangular configuration of the LEDs 316. Note that a rectangularconfiguration for the LEDs 316 is not required and that in fact, atrapezoidal configuration for the LEDs 316 may be preferred in order touniquely distinguish the orientation of the localization frame 302.Support pin 306 passes through the upper base 308 and is essentiallyparallel to a linear axis defined by the elongated portion 318. Thepurpose of support pin 306 is to allow clamps to engage it so that thelocalization biopsy guide frame 300 can be placed in a particularposition relative to a body part in order to guide a biopsy needle.

[0120] In order to guide a biopsy needle, the localization frame 302 isfitted with a biopsy guide 304 which is mounted to the top of the upperbase 308 and held in place by a clamp 328 which engages the upper base308 via four screws 330. The upper base 308 is also provided with asemicircular channel 332 which forms a seat for receiving the biopsyguide 326. The guide 304 comprises a hollow tube 334 having a collar 336at one end thereof, which has a threaded radial opening for receivingset screw 338.

[0121] The base plate 310 is fitted with a connector 340 for engaging acable which is connected to the digitizer 114 for providing signals forenergizing the LEDs 316. FIG. 12G illustrates one preferred embodimentof a wiring diagram which interconnects the connector 340 and four LEDs.

[0122] The localization frame 302 is made of the same material as thereference frame 122, i.e., ULTEM 1000 black which is autoclavable. Thebiopsy guide 304 may be stainless steel or any other autoclavable metalor plastic material. As with the reference frame, the localization framemay be battery operated thereby avoiding the need for a cable or aconnector for engaging the cable.

[0123]FIGS. 13D and 13E illustrate another localization device in theform of a localization drill guide assembly 350. The assembly 350includes a localization frame 302 which is the same as the frame usedfor the localization biopsy guide frame 300, except that it does nothave a support pin 306. It does have a semicircular channel 332 in theupper base 308 which receives a handle and drill guide assembly 354instead of the biopsy guide tube assembly 304. Assembly 354 includes ahandle 356 which is used by the surgeon, doctor, technician or nurseconducting the procedure. Handle 356 has a bore 358 therein forreceiving a shaft 360 which is seated within the semicircular channel332. The shaft terminates into an integral collar 362 which supports adrill guide tube 364. The axis of the drill guide tube 364 is at anangle relative to the axis of the shaft 360 to assist in aligning thedrill guide tube 364 relative to the point at which the drill bit willbe entering the patient's body. In one preferred embodiment, handle anddrill guide assembly 354 is a standard off-the-shelf instrument which ismounted to the channel 332 of the localization frame 302. The handle anddrill guide assembly 354 may be a Sofamor Danek Part 870-705. Screws 366(having heads insulated with high temperature RTV compound) attach theshaft 360 to the upper base 308 of the localization frame 302 and holdthe shaft 360 in place within the channel 332. As noted above, theV-shaped portion 320 of the localization frame 302 forms an opening 368between its legs 322 and 324 so that the drill guide tube 364 may belocated therebetween and project downwardly from the plane generallydefined by the localization frame 302. This allows the surgeon to sightin the position of the drill guide tube 364 by looking through the tube.Connector 370 is similar to connector 340, except that it provides anangular engagement with the cable which allows for more freedom ofmovement of the localization drill guide assembly 350. As with thelocalization frame noted above, the frame itself is made of ULTEM 1000which is autoclavable. The handle may be wood, plastic, or any otherautoclavable material and the shaft, collar and drill guide may bemetal, plastic or other autoclavable material, such as stainless steel.FIG. 13K illustrates a preferred embodiment of the wiring diagram forthe localization drill guide assembly 350.

[0124]FIGS. 13F and 13G illustrate another localization device in theform of a drill yoke localization frame 400. This frame 400 includes alocalization frame 302 of the same configuration as the localizationframes for the localization biopsy guide frame 300 and the localizationdrill guide assembly 350. Projecting from the underside of the baseplate 310 is a support member 402 which also supports a drill yoke 404in a plane which is essentially perpendicular to the plane defined bythe localization frame 302. Yoke 404 is essentially a collar which fitsover the housing of a Rex drill and is fixedly attached thereto by a setscrew 406. The drill yoke localization frame 400 allows the drillhousing to be precisely positioned for use during surgery.

[0125] Support member 402 also supports a connector 408 for receiving acable which is connected to the digitizer control unit 114. Supportmember 402 has a hollow channel therein so that the connector 408 may beconnected to the wires 410 which connect to the LEDs 316. FIG. 13Jillustrates one preferred embodiment of a wiring connection between theLEDs 316 and the connector 408.

[0126]FIGS. 13H and 13I illustrate another localization device in theform of a ventriculostomy probe 500. Probe 500 includes a handle 502having a bore 504 therein for receiving a support shaft 506 which inturn supports a catheter guide tube 508 along an axis which is parallelto the axis of the handle 502. The handle includes three LEDs 510mounted along its top surface for communication with the camera array110. The handle 502 has a hollow channel terminating in a bore 512 forreceiving a connector 514. The connector 514 is connected to wires 516which are also connected to the terminals of the LEDs 510. FIG. 13Jillustrates one preferred embodiment of a wiring diagram forinterconnecting the connector 514 and the LEDs 510. In operation, thetube 508 is positioned within the body, the brain for example, so that acatheter may be inserted within the body. Tube 508 includes a top slot518 which allows a catheter to be inserted therein. Preferably, the tubetip at its center is collinear with the chip height of all three LEDs510 so that a linear axis is defined therebetween. Based on this linearaxis and the predetermined knowledge of the distance between the tip andthe LEDs 510, the camera array 110 and digitizer 114 can determine theposition of the tip at any instant during a surgical or medicalprocedure.

[0127] The system of the invention may be used in the following manner.A reference frame is attached to a body part. For example, cranialreference arc frame 122 may be attached directly to a head via a headclamp such as a Mayfield clamp or spine reference arc frame 200 may beattached directly to a spinous bone via thoraco-lumbar mount 212.Thereafter, movement of the body part will result in correspondingmovement of the attached reference frame. The position of the body partmay be tracked by energizing the LEDs of the reference frame to providea signal to the camera array 110 so that the array can determine andtrack the position of the reference frame and, consequently, theposition of the body part.

[0128] A localization frame is used to precisely position an instrumentrelative to the body part. For example, a localization biopsy guideframe 300 may be used to position a biopsy needle relative to the bodypart. Alternatively, a localization drill guide assembly 350 may be usedto position a drill bit relative to the body part. Alternatively, adrill yoke localization frame 400 may be used to position a drillrelative to the body part. Alternatively, a ventriculostomy probe 500may be used to position a catheter relative to a body part. The positionof the instrument may be tracked by energizing the LEDs of thelocalization frame to provide a signal to the camera array 110 so thatthe array can determine and track the position of the localization frameand, consequently, the position of the instrument.

[0129] During calibration of the system, the position of the referenceframe relative to the body part is determined. Markers used during thepreoperative scan are located and identified in coordinates of thesurgical space as defined by the reference frame. Note that anatomiclandmarks may be used as markers. This provides a relationship betweenthe preoperative scan space and the surgical space. Once thisrelationship is established, the system knows the position of thepreoperative scans relative to the reference frame and thus can generatescans which illustrate the position of the localization frame and theinstrument relative to the body part. In other words, the systemaccomplishes image guided surgery. The system is ideally suited forlocating small, deep-seated vascular lesions and tumors and for reducingthe extent of the microsurgical dissection. It is also useful inidentifying boundaries. For example, suppose a surgeon is trying toidentify a boundary between normal brain and large supratentorialgliomas, which may be clearly shown on the preoperative scans but whichmay be difficult to visually locate in the operating room during aprocedure. The surgeon would take a localization probe and position it apoint near the boundary. The LEDs of the reference frame andlocalization probe are fired by use of the foot switch 116. As a result,the monitor 106 would provide a screen showing the position of the proberelative to a preoperative scan. By referring to the monitor, thesurgeon can now determine the direction in which the probe should bemore to more precisely locate the boundary. One the boundary is located,microcottonoid markers can be placed at the boundary of the tumor asdisplayed on the monitor before resection is started. The placement ofventricular catheters for shunts, ventriculostomy, or reservoirs is alsofacilitated by the use of the system, especially in patients who havesmall ventricles or who have underlying coagulopatby (e.g., liverfailure, acquired immunodeficiency syndrome) that makes a single passdesirable. The system can also be useful for performing stereotacticbiopsies. For further information regarding the system, see thefollowing articles which are incorporated herein by reference in theirentirety: Germano, Isabelle M., The NeuroStation System forImage-Guided, Frameless Stereotaxy, Neurosurgery, Vol. 37, No. 2, August1995. Smith et al., The Neurostation™-A Highly accurate, MinimallyInvasive Solution to Frameless Stereotactic Neurosurgery, ComputerizedMedical Imaging and Graphics, Vol. 18, No. 4, pp. 247-256, 1994.

[0130] In view of the above, it will be seen that the several objects ofthe invention are achieved and other advantageous results attained.

[0131] As various changes could be made in the above constructions,products, and methods without departing from the scope of the invention,it is intended that all matter contained in the above description andshown in the accompanying drawings shall be interpreted as illustrativeand not in a limiting sense.

[0132] In view of the above, it will be seen that the several objects ofthe invention are achieved and other advantageous results attained.

[0133] As various changes could be made in the above without departingfrom the scope of the invention, it is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. A system for use during a medical or surgicalprocedure on a body, said system generating a display representing theposition of one or more body elements during the procedure based onscans taken of the body by a scanner prior to the procedure, the scanhaving reference points for each of the body elements, the referencepoints of a particular body element having a known spatial relation tothe particular body element, said system comprising: means foridentifying, during the procedure, the position of the reference pointsof each of the body elements to be displayed; a processor modifying theimage data set according to the identified position of the referencepoints during the procedure, as identified by the identifying means,said processor generating a displaced image data set representing theposition and geometry of the body element(s) during the procedure; and adisplay utilizing the displaced image data set generated by theprocessor, illustrating the position and geometry of the body element(s)during the procedure.
 2. The system of claim 1 wherein the referencepoints in relation to the body elements and further comprising: amedical or surgical instrument, probe, or radiation delivery system;means for identifying, during the procedure, the position of medical orsurgical instrument relative to one or more of the body elements; andwherein the display is responsive to the medical or surgical instrumentposition identifying means to illustrate during the procedure therelative position of the body elements relative to the medical orsurgical instrument or focal point thereof.
 3. The system of claim 2wherein the medical or surgical instrument position identifying meansdetermines an orientation of the medical or surgical instrument relativeto the body elements and wherein the display illustrates the orientationof the medical or surgical instrument relative to the body elements. 4.The system of claim 1 wherein the identifying means comprises: areference array having a location outside the body for providing areference; and means for determining the position of the referencepoints of the body elements to be displayed relative to the referencearray.
 5. The system of claim 4 further comprising a registration probein communication with the reference array and wherein the determiningmeans is adapted to determine the position of a tip of the registrationprobe relative to the reference array whereby the position of thereference points of the body elements can be determined by positioningthe tip of the registration probe at each of the reference points. 6.The system of claim 5 wherein the reference array includes sensors andwherein the registration probe includes emitters communicating with thesensors of the reference array to indicate the position of theregistration probe relative to the reference array.
 7. The system ofclaim 5 wherein the registration probe includes sensors and wherein thereference array includes emitters communicating with the sensors of theregistration probe to indicate the position of the registration proberelative to the reference array.
 8. The system of claim 4 furthercomprising a reference frame having a position in known relation to oneof the body elements, said reference frame in communication with thereference array, and further comprising means for determining theposition of the reference frame relative to the reference array wherebythe body may be moved during the procedure while the body elementsremain in fixed relation to each other and in known relation to thereference frame so that the system can determine the position of each ofthe body elements after movement without again identifying the relativeposition of each of the reference points of each of the body elements.9. The system of claim 8 wherein the reference array includes sensorsand wherein the reference frame is attached to one of the body elementsand includes emitters communicating with the sensors of the referencearray to indicate the position of the reference frame relative to thereference array.
 10. The system of claim 8 wherein the reference frameincludes sensors and wherein the reference array is attached to one ofthe body elements and includes emitters communicating with the sensorsof the reference frame to indicate the position of the reference framerelative to the reference array.
 11. The system of claim 1 furthercomprising means for discriminating the body elements of the image dataset by creating an image data subset defining each of the body elements.12. The system of claim 11 wherein the processor translates each of theimage data subsets from the position of the body elements prior to theprocedure to the position of the body elements during: the procedurewhereby the displaced data set consists of the translated image datasubsets.
 13. The system of claim 11 wherein the identifying meanscomprises a device for determining a position of a contour of each ofthe body elements during the procedure and wherein the processorcompares the position of the contour of each of the body elements duringthe procedure as determined by the device to the position of the contourof each of the body elements prior to the procedure as represented bythe image data sub-set.
 14. The system of claim 13 wherein theidentifying means comprises an ultrasound probe for determining aposition of a contour of each of the body elements during the procedureand wherein the processor compares the position of the contour of theeach of the body elements during the procedure as determined by thedevice to the position of the contour of each of the body elements priorto the procedure as represented by the image data subset whereby thecontour of the body elements may be determined without the need forexposing the body elements.
 15. The system of claim 13 wherein theidentifying means comprises a scanner for determining a position of acontour of each of the body elements during the procedure and whereinthe processor compares the position of the contour of the each of thebody elements during the procedure as determined by the device to theposition of the contour of each of the body elements prior to theprocedure as represented by the image data subset.
 16. The system ofclaim 14 wherein said ultrasound probe has emitters thereon incommunication with the reference array and wherein the determining meansis adapted to determine the position of the ultrasound probe relative tothe reference array whereby the position of the contour of each bodyelement can be determined.
 17. The system of claim 14 wherein saidreference array has emitters thereon in communication with theultrasound probe and wherein the determining means is adapted todetermine the position of the ultrasound probe relative to the referencearray whereby the position of the contour of each body element can bedetermined.
 18. The system of claim 15 wherein said scanner has emittersthereon in communication with the reference array and wherein thedetermining means is adapted to determine the position of the scannerrelative to the reference array whereby the position of the contour ofeach body element can be determined.
 19. The system of claim 15 whereinsaid reference array has emitters thereon in communication with thescanner and wherein the determining means is adapted to determine theposition of the scanner relative to the reference array whereby theposition of the contour of each body element can be determined.
 20. Thesystem of claim 4 wherein the identifying means comprises a fluoroscopicdevice for determining a position of a projection of each of the bodyelements during the procedure and wherein the processor compares theposition of the projection of the each of the body elements during theprocedure to the position of the projection of each of the body elementsprior to the procedure.
 21. The system of claim 20 wherein thefluoroscopic device comprises a fluoroscopic tube in fixed relation to afluoroscopic plate between which the body elements are located fordetermining a position of a projection of each of the body elementsduring the procedure and wherein the processor compares the position ofthe projection of each of the body elements during the procedure to theposition of the projection of each of the body elements prior to theprocedure.
 22. The system of claim 21 wherein said fluoroscopic tube orsaid fluoroscopic plate each have emitters thereon in communication withthe reference array and wherein the determining means is adapted todetermine the position of the tube and plate relative to the referencearray whereby the position of the projection of each body element can bedetermined.
 23. The system of claim 21 wherein said reference array hasemitters thereon in communication with the fluoroscopic tube or thefluoroscopic plate and wherein the determining means is adapted todetermine the position of the tube or plate relative to the referencearray whereby the position of the projection of each body element can bedetermined.
 24. A method for use during a procedure, said methodgenerating a display representing the position of two or more bodyelements during the procedure based on an image data set generated priorto the procedure, which image data set has reference points for each ofthe body elements, said method comprising the steps of: identifying,during the procedure, the relative position of each of the referencepoints of each of the body elements to be displayed; modifying the imagedata set according to the identified relative position of each of thereference points during the procedure in order to generate a displacedimage data set representing the position of the body elements during theprocedure; and generating a display based on the displaced image dataset illustrating the relative position of the body elements during theprocedure.
 25. The method of claim 24 further comprising the step ofrepositioning the body elements so that the display based on thedisplaced data set representing the position of the body elements duringthe procedure is substantially the same as the display based on theimage data set generated prior to the procedure whereby the position ofthe body elements after repositioning is substantially the same as theposition of the body elements prior to the procedure when the image dataset was generated.
 26. The method of claim 24 wherein the referencepoints are part of the body elements and further comprising the stepsof: providing a medical or surgical instrument; identifying, during theprocedure, the position of medical or surgical instrument relative toone or more of the body elements; and generating a display based on theposition of the medical or surgical instrument illustrating the relativeposition of the body elements and the medical or surgical instrumentduring the procedure.
 27. The method of claim 26 further comprising thesteps of determining an orientation of the medical or surgicalinstrument relative to the body elements and generating a displayillustrating the orientation of the medical or surgical instrumentrelative to the body elements.
 28. The method of claim 24 furthercomprising the steps of: providing a reference array having a locationoutside the body for providing a reference; and determining the positionof the reference points of the body elements to be displayed relative tothe reference array.
 29. The method of claim 28 further comprising thesteps of providing a registration probe in communication with thereference array and determining the position of the reference points ofthe body elements by positioning the tip of the registration probe ateach of the reference points.
 30. The method of claim 28 furthercomprising the steps of proving a reference frame having a position infixed relation to one of the body elements, said reference frame incommunication with the reference array, and determining the position ofthe reference frame relative to the reference array whereby the body maybe moved during the procedure while the body elements remain in fixedrelation to each other and the reference frame so that the method candetermine the position of each of the body elements after movementwithout again identifying the relative position of each of the referencepoints of each of the body elements.
 31. The method of claim 24 furthercomprising the step of discriminating the body elements of the imagedata set by creating an image data subset defining each of the bodyelements.
 32. The method of claim 31 further comprising the step oftranslating each of the image data subsets from the position of the bodyelements prior to the procedure to the position of the body elementsduring the procedure whereby the displaced data set comprises thetranslated image data subsets.
 33. The method of claim 31 comprising thesteps of determining a position of a contour of each of the bodyelements during the procedure and comparing the position of the contourof the each of the body elements during the procedure to the position ofthe contour of each of the body elements prior to the procedure asrepresented by the image data set.
 34. The method of claim 24 whereinthe identifying step comprises the steps of positioning the bodyelements between a fluoroscopic tube and a fluoroscope plate in fixedrelation to the tube, energizing the tube to generate a projection ofeach of the elements on the plate, determining the relative position ofthe fluoroscopic projection of each of the body elements during theprocedure and comparing the position represented by the fluoroscopicprojection of each of the body elements during the procedure to therelative position of the body elements prior to the procedure.
 35. Amethod for use with two or more body elements which each have referencepoints, said method comprising the steps of: prior to a procedure:placing the body elements in a frame to fix their relative position; andscanning the fixed body elements; and during the procedure: placing thebody elements in the frame so that the body elements have the samerelative position as their position during scanning; determining theposition of reference points on the body elements relative to referencemeans; determining the position of a medical or surgical instrumentrelative to the reference means; determining the position of the medicalor surgical instrument relative to the body elements; and generating adisplay based on the pre-procedural scanning illustrating the determinedposition of the medical or surgical instrument relative to the bodyelements.
 36. The method of claim 35 wherein the frame can be activatedto move the body elements and further comprising the steps ofdetermining the relative position of the body elements during theprocedure and activating the frame to move the body elements so that therelative position of the body elements during the procedure correspondsto the relative position of the body elements during the scan prior tothe procedure.
 37. The system of claim 8 wherein the reference arrayincludes sensors and wherein the reference frame is comprised of adevice which is capable of continuously or periodically detecting andtracking one or more of the body elements and includes emitterscommunicating with the sensors of the reference array to indicate theposition of the reference frame relative to the reference array.
 38. Thesystem of claim 11 wherein the processor transforms each of the imagedata subsets representing the position and shape of the body elementsprior to the procedure to represent the position and shape of the bodyelements during the procedure whereby the displaced data set consists ofthe transformed image data subsets.
 39. The system of claim 2 whereinthe processor monitors the position of the instrument, probe orradiation delivery system and deactivates it when the monitored positionindicates that it is outside a predefined safe zone.
 40. The system ofclaim 2 further comprising robotics to control the position of theinstrument, probe or radiation delivery system and wherein the processorwould monitor the position of the instrument and instruct the roboticsto control it in a predetermined manner.
 41. A device for use with asurgical navigation system having a sensor array which is incommunication with the device to identify its position, said devicecomprising: a base member having a cavity therein; a plurality of lightemitting diodes on the base member, said diodes emitting light, whenactivated, for communicating with the sensor array of the surgicalnavigation system; an activating circuit connected to the diodes forproviding signals for activating the diodes; and wires located in thecavity of the base member and electrically interconnecting the powersupply and the light emitting diodes and for transmitting the signalsfor activating the diodes.
 42. A device for use with a surgicalnavigation system having a sensor array which is in communication withthe device to identify its position, the device for engaging a structureattached to or an instrument in known relation to a body part therebyproviding a known reference relative to the body part, the device havinga connector for engaging a cable connected to the surgical navigationsystem, the cable for providing signals for activating the device, saiddevice comprising: a base member having a cavity therein; a coupling onthe base member for engaging the structure in order to maintain the basemember in fixed relation to the body part thereby providing the fixedreference; a plurality of light emitting diodes on the base member, saiddiodes, when activated, emitting light for communicating with the sensorarray of the surgical navigation system; a connector attached to thebase member and adapted to engage the cable connected to the surgicalnavigation system, said connector for receiving the signals foractivating the diodes; and wires located in the cavity of the basemember and electrically interconnecting the connector and the lightemitting diodes and for transmitting the signals received by theconnector to the diodes to activate the diodes.
 43. The device of claim42 wherein the base member comprises an arc-shaped member and whereinthe coupling comprises a fitting for engaging a head clamp such as aMayfield clamp adapted to engage a head of a patient.
 44. The device ofclaim 43 further comprising spring clamps on the arc-shaped member forengaging a retractor arm for engaging the head and assisting in asurgical or medical procedure to be performed on the head.
 45. Thedevice of claim 42 for engaging a thoraco-lumbar mount adapted to engagea spinal bone of a patient wherein the base member comprises a generallyU-shaped member and wherein the coupling comprises a variable positionconnector for engaging the thoraco-lumbar mount so that the U-shapedmember can be positioned to form various angles relative to the mount.46. A device for use with a surgical navigation system having a sensorarray which is in communication with the device to identify itsposition, the device for guiding an instrument for engaging a body partthereby locating the instrument at a known position relative to the bodypart, the device having a connector for engaging a cable connected tothe surgical navigation system, the cable for providing signals foractivating the device, said device comprising: a housing having a cavitytherein; a structure on the housing for guiding the instrument in orderto maintan the instrument in a relationship relative to the housing; aplurality of light emitting diodes on the housing, said diodes, whenactivated, emitting light for communicating with the sensor array of thesurgical navigation system; a connector attached to the housing andadapted to engage the cable connected to the surgical navigation system,said connector for receiving the signals for activating the diodes; andwires located in the cavity of the housing and electricallyinterconnecting the connector and the light emitting diodes and fortransmitting the signals received by the connector to the diodes toactivate the diodes.
 47. The device of claim 46 further comprising aguide tube mounted on the housing for receiving a biopsy instrument anda support member projecting from the housing for engaging a clamp whichmaintains the housing in a relatively fixed position.
 48. The device ofclaim 46 further comprising a handle attached to the housing and a guidemember having a opening therein for receiving a drill bit.
 49. Thedevice of claim 46 further comprising a yoke attached to the housing andhaving a opening therein for receiving a drill bit.
 50. The device ofclaim 46 further comprising a guide tube attached to the housing andhaving a opening therein for receiving a catheter.
 51. The device ofclaim 46 further comprising a depression in the housing for receiving aprobe used in combination with the surgical navigation system forcalibrating the system and the device.
 52. A device for use with asurgical navigation system having a sensor array which is incommunication with the device to identify its position, the device foruse in guiding a catheter, the device for engaging a cable connected tothe surgical navigation system, the cable for providing signals foractivating the device, said device comprising: a handle having a cavitytherein; a plurality of light emitting diodes on the handle, said diodesemitting light, when activated, for communicating with the sensor arrayof the surgical navigation system; a connector attached to the handleand adapted to engage the cable connected to the surgical navigationsystem, said connector for receiving the signals for activating thediodes; wires located in the cavity of the handle and electricallyinterconnecting the connector and the light emitting diodes and fortransmitting the signals received by the connector to the diodes; and aguide member connected to the handle for guiding the catheter.
 53. Asurgical navigation system comprising: a controller; a sensor array; areference frame in communication with the array to identify itsposition; and a localization frame in communication with the array toidentify a position of the localization frame, the localization framefor guiding the instrument for engaging the body part thereby locatingthe instrument at a known position relative to the body part, thelocalization frame connected to the controller which provides signalsfor activating the localization frame.
 54. The system of claim 53wherein the reference frame comprises: a base member having a cavitytherein; a plurality of light emitting diodes on the base member, saiddiodes emitting light, when activated, for communicating with the sensorarray of the surgical navigation system; an activating circuit connectedto the diodes for providing signals for activating the diodes; and wireslocated in the cavity of the base member and electricallyinterconnecting the power supply and the light emitting diodes and fortransmitting the signals for activating the diodes.
 55. The system ofclaim 53 wherein the localization frame comprises: a housing having acavity therein; a structure on the housing for guiding the instrument inorder to maintain the instrument in a relationship relative to thehousing; a plurality of light emitting diodes on the housing, saiddiodes, when activated, emitting light for communicating with the sensorarray of the surgical navigation system; a connector attached to thehousing and adapted to engage the cable connected to the surgicalnavigation system, said connector for receiving the signals foractivating the diodes; and wires located in the cavity of the housingand electrically interconnecting the connector and the light emittingdiodes and for transmitting the signals received by the connector to thediodes to activate the diodes.